Document Type : Research Article
Authors
Department of Biosystems Engineering, University of Mohaghegh Ardabili, Ardabil, Iran
Abstract
Introduction: In many rural areas, manual threshers are still in use because of the small farming units. However, research sections, have been used manual threshers particularly in breeding unites in many cases due to the low volume of crop. Manual threshers for the first time were manufactured by Iran Ashtad Cooperative in two models (T25 and T30) and then they were made available to the farmers across the country. The threshers due to having wire loop drum had a good performance for threshing rice crop. According to the mentioned application, manual threshers expected to have been capable of threshing wheat crop. A type of this thresher (modelT30) was available in University of Mohaghegh Ardabili. Therefore, It was decided that the performance of this thresher was assessed at threshing some common wheat varieties in Ardabil province. Effects of drum speed levels (800, 900 and 1000 rpm) of threshing unit of john deere combine (model 955) on damaged grains percent showed that the minimum of this dependent factor was obtained at two levels of drum speed 800 and 900 rpm, clearance between drum and concave 25 mm and forward speed 1.8 km.h-1 (Lashgari et al., 2008). Research performed by Vejasit and Salokhe (2004) on a axial flow thresher revealed that the threshing efficiency can be 98 to 100% at tests for soybean, drum speed 600 to 700 rpm, feed rate 540 to 720 kg h-1 and grain moisture content 14.34 to 22.77 w.b.%. Alizadeh and Khodabakhshipour (2010) found at moisture content 17 to 23 w.b.% and drum speed 450 to 850 rpm at test of an axial flow thresher on paddy, ,the most damaged grains percent obtained at the most level of drum speed 850 rpm and the least level grain moisture content 17 W.b.%. Threshing losses due to mechanical damaged wheat grains during threshing process were reported 5.0, 8.1, 10.0 and 19.9% at tests at drum speed 800, 900, 1000 and 1100 rpm, respectively, by King and Riddols (1962). The results of research reported by Mitchell and Roundthwaite (1964) on investigation of two varieties of wheat resistance at grain moisture content 15 to 25 w.b.% and drum speed levels 17 to 36 m s-1 showed that damaged grains percent mean were 94.8 and 86.8 % at tests at the least and most drum speed levels.
Materials and Methods: The tests were accomplished with three varieties wheat (Azar2, Sardari and Rasad), three speed drum levels (400, 500, 600rpm) and three feed rate levels (600, 900, 1800 kg h-1). Grain moisture content varied from 12 to 13 w.b. %. For supplying requirement powerof thresher, AMitsubishi diesel motor (13.5 hp) was used. Preliminary tests on these wheat varieties showed that this thresher did not have desired threshing efficiency. Therefore, it was decided to use of a concave with less curvature radius. So that the minimum distance between the drum and concave was 6 mm. For adjustment of drum speed, a digital tachometer (Lutron DT-2236) was used some pulleys were used for transmission power from engine to drum shaft, The weight of each sample was 1 kg. To create different levels of feed rate, crop feeding times were considered 2, 4 and 6 seconds. The factorial experiment in a randomized complete block design has been used for analyzing data, Data mean comparison was done by Duncan's Multiple Test.
Results and Discussions: The results of analysis variance showed that effects of variety of the drum speed and feed rate were significant on threshing losses. Damaged grain percent was negligible. The results of mean comparison showed that the most (15.632%) and the least (4.154%) threshing losses obtained at tests on Azar2 and Rasad varieties, respectively. As increasing feed rate from 600 to 1800 kg h-1, threshing losses was decreased significantly. It was due to clusters compression at between drum and concave. The results of mean comparison of triplet interactions showed that the lowest threshing losses (0.147%) obtained at tests on Rasad variety, feed rate of 600 kg h-1 and rotational speed drum level of 600 rpm. the highest threshing losses (39.387%) obtained at tests on Azar2 variety, feed rate 1800 kg h-1 and rotational speed drum level of 400 rpm.
Conclusions:
1. Modified thresher was not able to thresh Azar2 variety. But it was able to thresh Sardary and Rasad wheat varieties with desirable threshing efficiency.
2. According to low and high threshing losses at tests on Rasad and Azar2 varieties, respectively, It must be conclude that shattering of Rasad variety is very high.
3. Damaged grain percent was negligible at test on each three varieties.
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